A few years ago I won a lot of cone yarn on eBay. Unfortunately, when it arrived I discovered it was 'industrial' yarn which is about the thickness of heavy thread. I recently started plying this cone yarn into a knittable thickness and it's working very well. I now have some skeins of lovely soft yarn. Now for my question. I know that after I spin wool I need to wash and soak it in hot soapy water but these skeins aren't all wool. Some are 100% acrylic some are 75% cotton/25% acrylic, some are 100% cotton and some are 75%wool/25% acrylic. After plying do I need to wash and soak the skeins to set the twist or is that only reserved for newly spun wool?